Modified SBA-15 matrices for high-throughput screening of melamine in milk samples by MALDI-TOF MS

Matrix-assisted laser-desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) works inefficiently on small molecules because of the interference of matrix-related peaks in low m/z regions. A modified SBA-15 matrix, ([CHC−] [NH3+-Si-SBA-15-Si-NH3+] [CHC−]), was synthesized by covalently attaching SBA-15 to an ionic liquid formed by α-cyano-4-hydroxy cinnamic acid (CHCA) and 3-APTES. Compared with CHCA and ([SBA-15-Si-NH3+] [CHC−]), [CHC−] [NH3+-Si-SBA-15-Si-NH3+] [CHC−] demonstrated several advantages in melamine analysis, such as minimal background interference ions, high homogeneity, and improved sensitivity and reproducibility. Using the new matrix, we developed a high-throughput screening method for the detection of melamine in milk samples by MALDI-TOF MS. The influence of various parameters, such as solvent, concentration of the matrix suspension, the ratio between matrix and sample, deposition strategy, drying methods, and sample preparation method, were also investigated. Under optimized conditions for melamine determination in milk samples, a low detection limit (0.10 mg/kg) and high reproducibility (RSD ≤ 14%) were obtained.

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► A new modified SBA-15 matrix applied to MALDI-TOF MS was synthesized.
► The matrix decreased chemical noise and improved analyte signal intensity.
► A high-throughput screening method of melamine was developed with the new matrix.